1. Field of the Invention
The present invention relates to a dumping device and a dumping method for unloading used catalyst adhered and agglomerated inside a reactor of petroleum refining plant, chemical plant and the like.
2. Description of Related Art
Various catalysts are used in a petroleum refining plant, chemical plant and the like for facilitating chemical reactions. The catalysts are used being filled inside a reactor for circulating fluid material.
Such catalysts have to be periodically unloaded from the reactor to be exchanged, since activity of the catalyst gets weak as the catalysts are poisoned by sedimentation of carbide, metal or the like and the catalysts are smashed on account of lowering of mechanical strength. The catalysts also need to be unloaded from the reactor for repairing or examining the plant.
[Unloading Condition of Catalyst]
The catalysts need to be unloaded in a short time period for minimizing plant shut-down time.
Further, since the catalyst in operation is often in a reducing atmosphere, carbide, sulfur etc. adhered to the catalyst while the catalyst is used can generate heat on account of oxidization of the catalyst when the catalyst is made open to the air for exchanging the catalyst. Accordingly, the unloading work has to be appropriately performed considering accompanying bad influence of the heat, and, further, dust of the catalyst on human body.
Further, nitrogen gas is supplied into the reactor for preventing ignition caused by oxidization of the catalyst when the reactor is big, so that the work is conducted under nitrogen gas atmosphere.
[Actual Catalyst Unloading]
Conventionally, following methods are known for unloading the catalyst from the reactor.
(1) Unloading the catalyst from catalyst dumping nozzle provided on a lower part of the reactor.
(2) Vacuum unloading the catalyst from a manhole provided onto a top part of the reactor.
Which one of the above methods should be selected is determined by a supervisor after opening the catalyst dumping nozzle of the reactor to examine whether the inside catalyst can be unloaded or not. When the catalyst is not agglomerated and can be unloaded from the catalyst dumping nozzle, the unloading work is conducted according to above (1) method.
On the other hand, when the catalyst is agglomerated and can not be unloaded from the catalyst dumping nozzle, the unloading work is performed according to above (2) method. In other words, after discharging reacting material such as crude oil before the vacuum unloading, the agglomerated catalyst is smashed using a spade etc., or alternatively, a pick etc. driven by air or oil pressure when the catalyst is especially agglomerate. Subsequently, the smashed and powdered catalyst is sucked in by a vacuum hose and the like from the manhole side to discharge to a hopper etc.
[Problem in Unloading Catalyst]
Though the catalyst in the reactor is agglomerated, the carbide and the like adhered to the catalyst can be oxidized to generate heat when the catalyst is made open to the air. In this case, the unloading work is difficult on account of a high temperature of the reactor. Further, when the work is carried out in the nitrogen gas atmosphere, the unloading work is difficult to be performed in the reactor. Accordingly, long time is necessary for the unloading work of the catalyst inside the reactor, so that the work efficiency is deteriorated and the plant shut-down time is prolonged.
Further, according to the conventional vacuum unloading method, the catalyst dumping nozzle is opened to examine whether the catalyst can be discharged therefrom. Consequently, when the catalyst can not be discharged from the catalyst dumping nozzle, the unloading process has to be changed to perform the vacuum unloading using the vacuum hose from the upper manhole. Accordingly, the work efficiency is bad for the extra process. Further, since the catalyst is sucked in by the vacuum hose while smashing the catalyst, the catalyst has to be smashed considerably small and the vacuum hose has to be drawn to the smashed spot. Therefore, a plurality of workers are necessary, thereby further deteriorating work efficiency.
According to the conventional vacuum unloading method, a special vacuum apparatus is necessary, thereby requiring extra costs.
Since the catalyst is sucked at an intense speed according to the conventional vacuum unloading method, the catalyst is often smashed to cause almost 20% catalyst loss, thereby causing bad yield rate for recycling the catalyst.